Magnetic sensing of currency is not new, and the art is highly developed. One device, described in the U.S. Pat. No. 3,180,491 includes means for advancing successive bills past a sensor at a substantially uniform rate, whereby the signals generated by examining the centrally disposed portrait may be compared with those of a genuine bill. Others are equally complicated, and are designed principally for use in financial institutions where a large volume of currency is examined on a daily basis. Such devices are now only incapable of being conveniently transported, but, because of mechanical complexity, are extremely expensive to manufacture.